1. Technical Field
The present invention pertains to devices for warming intravenous (IV) solution during infusion into a patient. In particular, the present invention pertains to a device for receiving and heating a preformed IV tubing cassette or cartridge connected to an IV line to warm solution flowing within the line to a desired temperature during infusion into a patient.
2. Discussion of Related Art
Intravenous (IV) fluids are typically infused into a patient utilizing a liquid filled bag or container and an IV fluid line. The fluids are generally delivered from the container to the patient via gravitational forces and/or applied pressure. It is important in many situations that the temperature of the fluid within the IV line be maintained within a desirable and safe temperature range upon entering the patient body so as to eliminate any potential for thermal shock and injury to the patient.
Accordingly, the related art provides several devices for controlling the temperature of fluid in an IV line for infusion into a patient. For example, U.S. Pat. No. 4,167,663 (Granzow, Jr. et al.) discloses a blood warming device including a housing with a heating compartment and an access door. The heating compartment includes a warming bag that is internally baffled to define a tortuous flow path and has an inlet port and an outlet port for allowing fluid to flow through the bag. The bag is sandwiched between a plate on the access door and an opposing plate within the heating compartment. The two plates include heating elements to heat the bag and the fluid flowing therein. The device further includes temperature sensors to measure the temperature of fluid flowing within the bag and control circuitry to control the heating elements in accordance with the measured temperatures.
U.S. Pat. No. 4,356,383 (Dahlberg et al.) discloses a fluid heating apparatus including a box-shaped member having an enclosure member or cap, a conduit or bag disposed between the box-shaped member and cap and a pair of heating plates respectively connected to the box-shaped member and cap to abut opposing sides of the conduit and heat fluid flowing therethrough. A temperature sensing device is positioned for engaging the conduit at a predetermined location to sense the temperature of fluid within the conduit. The apparatus further includes a contact member to engage the conduit at a predetermined location for compressing the conduit to constrict the cross-sectional area of the flow passage when the flow rate of fluid is below a predetermined flow rate.
U.S. Pat. No. 5,245,693 (Ford et al.) discloses an apparatus for heating parenteral fluids for intravenous delivery to a patient. The apparatus includes a disposable cassette which is made up of a unitary member divided to form a serpentine flow path by a plurality of path separators. Thin, flexible metallic foil membranes are sealingly joined to the unitary member on the upper and bottom surfaces thereof to form an enclosed, fluid-tight serpentine flow path between the plurality of path separators. The entire periphery of the unitary member and heat conductive foil membranes are sealingly held by a framework. The disposable cassette slides between first and second heating blocks which contact the heat conductive foil membranes so as to provide heat transfer to fluid flowing in the serpentine flow path. The heating blocks are designed to provide a gradation of heat energy where more heat is energy is available for transfer to the fluid at the inlet end of the serpentine flow path than that available for transfer to the fluid at the serpentine flow path outlet end.
U.S. Pat. No. 5,381,510 (Ford et al.) discloses a disposable, in-line heating cassette and apparatus for raising the temperature of fluids. The cassette comprises a spacer defining a sinuous or serpentine flow pathway interposed between flexible foils and mounted on a frame. The frame comprises inlet and outlet tubes and related input and output parts which communicate with the serpentine path. Juxtaposed heating plates in direct contact with the cassette substantially contact the entire heating surface of the foils, thereby providing a thermal path from the heating plate to the foil and further to the fluid. The heating plates have several electrically conductive strips thereon for generating a gradation of heat energy where more heat energy is available for transfer at the inlet end than at the outlet end of the serpentine flow path.
U.S. Pat. No. 6,175,688 (Cassidy et al.) discloses an intravenous fluid heater dimensioned to be wearable adjacent a patient intravenous fluid infusion situs. The heater includes a heat exchanger for defining a flow path through the heater for fluid to be infused via the infusion situs. At least one controllable heating element is provided for heating the fluid in the flow path by heat conduction thereto through the heat exchanger. Sensors are included for sensing respective temperatures of entering and exiting fluids of the flow path. A controller controls heating of the fluid in the flow path based on temperatures of the exiting fluids to cause the fluid in the flow path to be substantially uniformly heated to a desired infusion temperature prior to exiting the heater.
U.S. Pat. No. 6,261,261 (Gordon) discloses an infrared heating device for prewarming solutions that includes a cassette having a predetermined length of tubing connectable between an IV solution source and an infusion site for a patient. An infrared energy-generating sheet is positioned onto the cassette adjacent the IV tubing. In one embodiment of the device, the IV tubing is arranged in a spiral path on the cassette.
The related art devices described above suffer from several disadvantages. In particular, the Granzow, Jr. et al., Dahlberg et al., Ford et al. and Cassidy et al. devices each generally employ housings that inhibit viewing of fluid during treatment. Thus, the fluid may incur certain undesirable conditions within the devices (e.g., contamination, air bubbles, etc.) that are beyond the view of, and may be undetected by, an operator, thereby risking serious injury to a patient. Further, these devices tend to employ heat exchangers generally with a serpentine fluid flow path defined therein that typically includes a plurality of overlapping fluid flow passageways. The path generally includes dimensions different than those of the fluid lines, thereby tending to affect the rate of fluid flow and, consequently, the amount of thermal energy required to heat the fluid to a desired temperature. As a result, the devices may need to further employ flow sensors to measure and account for changes in fluid flow in order to ensure maintenance of proper fluid temperature, thereby increasing system complexity and costs. Moreover, the overlapping passageways tend to confine thermal energy that may otherwise be distributed to heat the fluid, thereby limiting the device heating potential. The Gordon device utilizes a cassette with a fluid flow path formed of tubing. However, this device employs infrared radiation to thermally treat the fluid, thereby involving special safety measures and requiring additional components to isolate the radiation from the patient. In addition, the above-described systems of the related art include heat exchangers or fluid flow paths including inlets separated from fluid outlets, thereby tending to increase complexity of connections and installation for use with an infusion apparatus.